#include <fstream>
using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");

int N;
bool c[2000005];

int main(){
    in >> N;
    for (int i = 2; i <= N; ++i){
        for (int j = 2; j <= N; ++j)
            if (i * j <= N) c[i*j] = 1;
            else break;
    }
    int suma = 0;
    for (int i = 2; i <= N; ++i)
        if (c[i] == 0)
            suma++;
    out << suma << '\n';
    return 0;
}